"It does not bode well," said Dr. Tipu Aziz, professor of neurosurgery at Oxford University who is not connected to Schumacher's care.

"The fact that he hasn't woken up implies that the injury has been extremely severe and that a full recovery is improbable."

Schumacher, 45, was skiing in the Alps when he hit his head on a rock. He was put into a medically induced coma and has undergone multiple operations. Citing a doctor who is a trustee for a British head injury charity, the Eurosport article said that Schumacher "probably would face significant disabilities because of the length of time he has already spent comatose."

Dr. Aziz also said that doctors typically try to bring someone out of a coma every few days.

Schumacher retired from Formula 1 after driving the 2012 season with Mercedes. He won five consecutive championships with Ferrari from 2000-04 before retiring for three seasons from F1 before returning in 2010.